The present invention relates to power supply generators for ultrasonic electromechanical transducers in general, and more particularly to such power supply generators as can be plugged into the common utilities network such as 110 volt/60 hertz in the United States or the 220 volt/50 hertz network more currently used in Europe. The invention is especially usable for ultrasonic cleaning applications, and could be used in conjunction with electromechanical transducers of the type described for instance in U.S. Pat. No. 3,406,302 issued on Mar. 15, 1966 to R. J. Lanyi et al.
Typically, such transducers are used in surface cleaning of workpieces by ultrasonic vibrations.
INdustrial applications of ultrasonic cleaning include: removing drawing-lubricants from carbon-steel wire for steel-belted tires, aluminum welding wire, alloy welding wire, stainless steel welding rods, stranded copper wire, magnet wire, and similar such drawn and extruded material; it is also known to use the ultrasonic cleaning method to clean copper-clad aluminum coaxial cable, to remove mill scale from steel wire rod and to clean integrated circuits and electrical connectors of longitudinal configuration. Typically, in ultrasonic cleaning, a transducer creates alternately low and high pressure conditions in a liquid preferably of low viscosity, to convey vibrations from the transducer to the workpiece to be cleaned. On the negative side of this alternating cycle, pressure is reduced to less than the vapor pressure of the liquid, forming microscopic voids or bubbles. A half cycle later, the pressure in this same zone becomes positive, and the vapor bubbles implode -- bursting inwardly -- a reaction which is called "cavitation." It is this cavitation, with the accompanying phenomena of pressure and heat at each point of implosion, that creates the "scrubbing" action in ultrasonic cleaning systems. This action, in conjunction with the proper liquid, provides a higly efficient cleaning method. The liquid selected for ultrasonic cleaning can be either a water-based (aqueous) solution or a solvent such as chlorinated hydrocarbons or Freon (solvent). When a solvent is used for cleaning, drying of the workpiece may be necessary to minimize solvent escape to the atmosphere for safety and health reasons, and to reduce operational costs by minimizing solvent losses. This involves a closed loop unit to recapture solvent from the drying air, condense it, and return it to the total system.
The fluid coupled between the active face of the transducer and the workpiece represent a load which as seen from the power supply enacting the transducer is reflected back in the form of an effective resistance which has to be accounted for in the generation of power at ultrasonic frequency to drive the transducer.
Moreover, the ultrasonic power supply generator is often used to drive several transducers in parallel in order to increase the utilization factor but also in order to be able to accommodate different workpieces at the same time.
Besides, another requirement for an ultrasonic power supply generator is to accommodate with the same power supply different transducer coils, in particular transducers of different power capability. As a result, the power supply generator must be capable with the internal circuit components to drive transducer coils of much different sizes and with loads falling within a wide power range.
An object of the present invention is with a given basic electrical circuitry and a given alternative current voltage source to provide a power supply generator of broadened ultrasonic power output range.
Another object of the invention is to provide a transformerless power supply generator which is effective to provide a given maximum ultrasonic power output with a 110 volt/60 hertz voltage source as well as with a 220 volt/50 hertz voltage source.